What is Gastroenteritis, or commonly known as Stomach Flu ?

[Extracted from the website of www.emedicinehealth.com]

Gastroenteritis is a condition that causes irritation and inflammation of the stomach and intestines (the gastrointestinal tract). Diarrhea, crampy abdominal pain, nausea, and vomiting are the most common symptoms.

Viral infection is the most common cause of gastroenteritis but bacteria, parasites, and food-borne illness (such as shellfish) can be the offending agent.

Many people who experience the vomiting and diarrhea that develop from these types of infections or irritations think they have "food poisoning," and they may indeed have a food-borne illness. Many people also refer to gastroenteritis as "stomach flu," although influenza has nothing to do with the condition.

Travelers to foreign countries may experience "traveler's diarrhea" from contaminated food and unclean water.

* The severity of infectious gastroenteritis depends on the immune system's ability to resist the infection. Electrolytes (these include essential elements of sodium and potassium) may be lost as you vomit and experience diarrhea.

* Most people recover easily from a short bout with vomiting and diarrhea by drinking fluids and easing back into a normal diet. But for others, such as infants and the elderly, loss of bodily fluid with gastroenteritis can cause dehydration, which is a life-threatening illness unless the condition is treated and fluids restored.

Causes

Gastroenteritis has many causes. Viruses and bacteria are the most common.

Viruses and bacteria are very contagious and can spread through contaminated food or water. In up to 50% of diarrheal outbreaks, no specific agent is found. Improper handwashing following a bowel movement or handling a diaper can spread the disease from person to person.

Gastroenteritis caused by viruses may last one to two days. On the other hand, bacterial cases can last for a longer period of time.

Viruses

Fifty to seventy percent of cases of gastroenteritis in adults are caused by the noroviruses.

Rotavirus is the leading cause of infection in children.

Other viruses that cause gastrointestinal symptoms include :

* Adenoviruses

* Parvoviruses

* Astroviruses

Bacteria

Bacteria may cause gastroenteritis directly by infecting the walls of the stomach and intestine. As well, some bacteria like Staphylococcus aureus can form a toxin that is the cause of symptoms. Staph is a common type of food poisoning.

Escherichia coli can cause significant problems, and one type of the bacteria, E. coli O157:H7 can also affect kidney function.

Salmonella, Shigella and Campylobacter are also common causes of illness.

* Salmonella - the cause of typhoid fever is contracted from handling poultry or reptiles such as turtles that carry the germs

* Campylobacter - from the consumption of undercooked meat, unpasteurized milk

* Shigella - typically spread from person to person

Clostridium difficile (C difficile) bacteria may overgrow in the large intestine after a patient has been on antibiotics for an infection.

Parasites and protozoans

These tiny organisms are less frequently responsible for intestinal irritation. You may become infected by one of these by drinking contaminated water. Swimming pools are common places to come in contact with these parasites. Common parasites include these:

* Giardia - The most frequent cause of waterborne diarrhea, causing giardiasis

* Cryptosporidium - Affects mostly people with weakened immune systems and causes watery diarrhea

Other common causes

Gastroenteritis that is not contagious to others can be caused by chemical toxins, most often found in seafood, food allergies, heavy metals, antibiotics, and other medications.

Symptoms

By definition, gastroenteritis affects both the stomach and the intestines, resulting in both vomiting and diarrhea.

Common symptoms may include :

* Low grade fever to 100°F (37.7°C)

* Nausea with or without vomiting

* Mild-to-moderate diarrhea:

* Crampy painful abdominal bloating

More serious symptoms

* Blood in vomit or stool

* Vomiting more than 48 hours

* Fever higher than 101°F (40°C)

* Swollen abdomen or abdominal pain

* Dehydration - weakness, lightheadedness, decreased urination, dry skin, dry mouth and lack of sweat and tears are characteristic findings.